Are lazy vars in Swift computed more than once?

lazy vars are only calculated once, the first time you use them. After that, they’re just like a normal variable.

This is easy to test in a playground:

class LazyExample {
    var firstName = "John"
    var lastName = "Smith"
    lazy var lazyFullName : String = {
        [unowned self] in
        return "\(self.firstName) \(self.lastName)"
    }()
}

let lazyInstance = LazyExample()

println(lazyInstance.lazyFullName)
// John Smith

lazyInstance.firstName = "Jane"

println(lazyInstance.lazyFullName)
// John Smith

lazyInstance.lazyFullName = "???"

println(lazyInstance.lazyFullName)
// ???

If you’ll want to recalculate it later, use a computed property (with a backing variable, if it’s expensive) – just like you did in Objective-C.